This invention relates to a die assembly for the cold drawing of wire and/or bar stock. Specifically, this invention relates to a pressure die holder assembly having venting means to decrease lubricant pressure within the pressure die holder.
Competitive pressures among wire manufactures has lead to increases in wire drawing speeds. In order to draw at high speeds, many wire manufactures use pressure applications to help increase wire lubrication and decrease temperatures. In the wire drawing process, it is common practice to continuously draw the wire stock through a die assembly which includes a pressure die, which forces lubricant under high pressure onto the wire surface, followed by a drawing die, which reduces the diameter of the wire. Forcing lubricant through the dies with the wire allows the die to run at much cooler temperatures while maintaining consistent lubricant residuals. Pressure die systems allow manufacturers to increase production without dramatically increasing die wear.
The pressure die holder which is now commonly used employs an elongate hollow cylindrical body, bisected lengthwise, which receives the two dies and holds them in series during the wire drawing process. The drawback with using this type of die holder is that the proper axial alignment of the dies difficult to maintain as the pressure between the dies becomes great.
U.S. Pat. No. 5,402,664 to Sarver et al discloses a cylindrical die holder for holding a pair of dies in axial alignment. A cap portion is threaded onto a body portion. This invention requires the use of specially designed dies rather than standard stock dies, and employs no pressure relief venting of the lubricant.